Optical cavities are used extensively to enhance processes that depend on the interaction between light and matter due to their strong frequency selectivity and sharp dispersion near resonance. Most of the cavities that are used in optics have relatively large dimensions and modest Qs (<10,000). a="" new="" type="" of="" optical="" resonator,="" which="" has="" been="" the="" focus="" of="" increased="" attention="" this="" year="" as="" a="" possible="" photonic="" device,="" is="" the="" spherical="" dielectric="" microparticle="">10,000).>